LEDs are becoming increasingly popular as a light source in decorative and Christmas lights due to their reliability, energy savings, longevity, and cool operation. Manufacturers of decorative light strings are constantly working to maximize the brightness and benefits of LEDs as a light source as well as reduce production cost to narrow the gap between traditional, incandescent and LED light string cost.
It is known in the art the use of a DC power supply to power LED lamps maximize LED brightness. It is further known in the art that reduction of DC ripple in a rectified (AC to DC) circuit is desirable to reduce peak voltage, placing stress on the LED lamps and thus shortening their lifespan.
FIG. 3 shows a prior art embodiment (U.S. patent application Ser. No. 10/836,062) of an LED lighting chain. The prominent feature of this prior art is circuit rectification wherein the rectifying diodes (31, 32, 33, 34) are installed in split pairs in an attempt to save wire, thus reducing cost.
FIG. 4 also shows a prior art embodiment (U.S. patent application Ser. No. 10/836,062) wherein multiple series connections (30) are employed. According to this embodiment of the invention the number of wires required in the manufacture of the light chain increases one-for-one with each parallel connection of LEDs in series added to the lighting chain. This defeats the wire saving purpose and creates an additional safety hazard.
The lighting chains shown in FIG. 3 and FIG. 4 would typically be rated for 3 Amps or 5 Amps. As parallel connections of series blocks are added the increased current flow through the rectifying diodes quickly overheat them causing a fire hazard. A load of only one Amp (⅓ to ⅕ of the circuit capacity) causes the rectifying diodes to overheat sufficiently to melt the surrounding plastic.